Nitric oxide (NO), a diffusible free radical gas, acts as a neurotransmitter in brain and peripheral nervous system.
It accounts for the activity of endothelium-derived relaxing factors, which stimulate vasodilatation by releasing NO from the endothelium.
Unlike typical neurotransmitter, NO is a not stored in synaptic vesicle and does not act on membrane receptors.
Synthesis of NO, initially demonstrated in vascular endothelium, is now found in many tissues.
NO is synthesized by L-arginine, oxygen, and NADPH by three known isoforms of heme-containing flavoproteins termed NO synthase (NOS, I-III, mol wt.
~130-160 kD).
One group of enzyme is constitutive, agonist-triggered, and dependent on Ca2+/Calmodulin and is inhibited by L-arginine analogues (L-NNA, L-NMMA).
It is found in endothelium, adrenal glands, brain and platelets.
The other principle group is inducible, Ca2+/Calmodulin-independent, and inhibited by NMMA and L-NNA.
It has been found in macrophage, hepatocytes, tumor cells, vascular smooth muscle and endothelial cells.
Analyses of cDNA clones have identified three distinct NOS genes in mammals: neuronal (nNOS/bNOS/NOS-I), endothelial (eNOS/NOS-III), and macrophage (mNOS/iNOS/NOS-II).
Both nNOS and eNOS are constitutive and the mNOS/iNOS is inducible.
Sequence homology among different cloned isoforms is ~ 50%.
Applications:Suitable for use in ELISA.
Western Blot, though not tested, may potentially be used as an application.
